Proton Pump Inhibitor Use and Efficacy of Nivolumab and Ipilimumab in Advanced Melanoma.

The impact of proton pump inhibitors (PPIs) on clinical outcomes with first-line immune checkpoint inhibitors (ICIs) in patients with metastatic melanoma was previously analyzed in the phase II study, CheckMate 069. This retrospective analysis utilized data from three phase II/III studies of first-line ICI therapy in untreated advanced melanoma: CheckMate 066, 067, and 069. All randomized patients with PPI use ≤ 30 days before initiating study treatment were included in the PPI-use subgroup. Possible associations between baseline PPI use and efficacy were evaluated within each treatment arm of each study using multivariable modeling. Approximately 20% of 1505 randomized patients across the studies reported baseline PPI use. The median follow-up was 52.6-58.5 months. Objective response rate (ORR), progression-free survival (PFS), and overall survival analyses provided insufficient evidence of a meaningful association between PPI use and efficacy outcomes with nivolumab-plus-ipilimumab, nivolumab, or ipilimumab therapy. In five of the six ICI treatment arms, 95% confidence intervals for odds ratios or hazard ratios traversed 1. Significant associations were observed in the CheckMate 069 combination arm between PPI use and poorer ORR and PFS. This multivariable analysis found insufficient evidence to support meaningful associations between PPI use and ICI efficacy in patients with advanced melanoma.

Advanced glycation end products in extracellular matrix proteins contribute to the failure of sensory nerve regeneration in diabetes.

OBJECTIVE: The goal of this study was to characterize glycation adducts formed in both in vivo extracellular matrix (ECM) proteins of endoneurium from streptozotocin (STZ)-induced diabetic rats and in vitro by glycation of laminin and fibronectin with methylglyoxal and glucose. We also investigated the impact of advanced glycation end product (AGE) residue content of ECM on neurite outgrowth from sensory neurons. RESEARCH DESIGN AND METHODS: Glycation, oxidation, and nitration adducts of ECM proteins extracted from the endoneurium of control and STZ-induced diabetic rat sciatic nerve (3-24 weeks post-STZ) and of laminin and fibronectin that had been glycated using glucose or methylglyoxal were examined by liquid chromatography with tandem mass spectrometry. Methylglyoxal-glycated or unmodified ECM proteins were used as substrata for dissociated rat sensory neurons as in vitro models of regeneration. RESULTS: STZ-induced diabetes produced a significant increase in early glycation N(epsilon)-fructosyl-lysine and AGE residue contents of endoneurial ECM. Glycation of laminin and fibronectin by methylglyoxal and glucose increased glycation adduct residue contents with methylglyoxal-derived hydroimidazolone and N(epsilon)-fructosyl-lysine, respectively, of greatest quantitative importance. Glycation of laminin caused a significant decrease in both neurotrophin-stimulated and preconditioned sensory neurite outgrowth. This decrease was prevented by aminoguanidine. Glycation of fibronectin also decreased preconditioned neurite outgrowth, which was prevented by aminoguanidine and nerve growth factor. CONCLUSIONS: Early glycation and AGE residue content of endoneurial ECM proteins increase markedly in STZ-induced diabetes. Glycation of laminin and fibronectin causes a reduction in neurotrophin-stimulated neurite outgrowth and preconditioned neurite outgrowth. This may provide a mechanism for the failure of collateral sprouting and axonal regeneration in diabetic neuropathy.

Reversal of hyperglycemia-induced angiogenesis deficit of human endothelial cells by overexpression of glyoxalase 1 in vitro.

Dicarbonyl glycation of RGD and GFOGER sites in type IV collagen has been associated with decreased angiogenesis. In this study, we investigated whether overexpression of glyoxalase 1 to decrease dicarbonyl glycation would prevent the angiogenesis deficit induced by hyperglycemia in vitro. Transfection of human microvascular endothelial cells resulted in a four-fold increase in glyoxalase 1 activity compared with controls. Incubation of human microvascular endothelial cells in model hyperglycemia produced a 32% decrease in formation of tube structures that was prevented by glyoxalase 1 overexpression. We conclude that increased protection against dicarbonyl glycation of endothelial cell protein protects hyperglycemia-induced angiogenesis deficit.

Increased dicarbonyl metabolism in endothelial cells in hyperglycemia induces anoikis and impairs angiogenesis by RGD and GFOGER motif modification.

Chronic vascular disease in diabetes is associated with disruption of extracellular matrix (ECM) interactions with adherent endothelial cells, compromising cell survival and impairing vasculature structure. Loss of functional contact with integrins activates anoikis and impairs angiogenesis. The metabolic dysfunction underlying this vascular damage and disruption is unclear. Here, we show that increased modification of vascular basement membrane type IV collagen by methylglyoxal, a dicarbonyl glycating agent with increased formation in hyperglycemia, formed arginine-derived hydroimidazolone residues at hotspot modification sites in RGD and GFOGER integrin-binding sites of collagen, causing endothelial cell detachment, anoikis, and inhibition of angiogenesis. Endothelial cells incubated in model hyperglycemia in vitro and experimental diabetes in vivo produced the same modifications of vascular collagen, inducing similar responses. Pharmacological scavenging of methylglyoxal prevented anoikis and maintained angiogenesis, and inhibition of methylglyoxal metabolism with a cell permeable glyoxalase I inhibitor provoked these responses in normoglycemia. Thus, increased formation of methylglyoxal and ECM glycation in hyperglycemia impairs endothelial cell survival and angiogenesis and likely contributes to similar vascular dysfunction in diabetes.

Peptide mapping identifies hotspot site of modification in human serum albumin by methylglyoxal involved in ligand binding and esterase activity.

Methylglyoxal is a potent glycating agent under physiological conditions. Human serum albumin is modified by methylglyoxal in vivo. The glycation adducts formed and structural and functional changes induced by methylglyoxal modification have not been fully disclosed. Methylglyoxal reacted with human serum albumin under physiological conditions to form mainly the hydroimidazolone N(delta)-(5-hydro-5-methyl-4-imidazolon-2-yl)-ornithine (92% of total modification) with a minor formation of argpyrimidine, N(epsilon)-(1-carboxyethyl)lysine, and methylglyoxal lysine dimer. When human serum albumin was modified minimally with methylglyoxal, tryptic peptide mapping indicated a hotspot of modification at Arg-410 located in drug-binding site II and the active site of albumin-associated esterase activity. Modification of Arg-410 by methylglyoxal was found in albumin glycated in vivo. Other sites of minor modification were: Arg-114, Arg-186, Arg-218, and Arg-428. Hydroimidazolone formation at Arg-410 inhibited ketoprofen binding and esterase activity; correspondingly, glycation in the presence of ketoprofen inhibited Arg-410 modification and loss of esterase activity. The pH dependence of esterase activity indicated a catalytic group with pK(a) = 7.9 +/- 0.1, assigned to the catalytic base Tyr-411 with the conjugate base stabilized by interaction with the guanidinium group of Arg-410. Modification by methylglyoxal destabilized Tyr-411 and increased the pK(a) to 8.8 +/- 0.1. Molecular dynamics and modeling studies indicated that hydroimidazolone formation caused structural distortion leading to disruption of arginine-directed hydrogen bonding and loss of electrostatic interactions. Methylglyoxal modification of critical arginine residues, therefore, whether experimental or physiological, is expected to disrupt protein-ligand interactions and inactivate enzyme activity by hydroimidazolone formation.